It can even drive a small motor or lamp with diodes added to protect from inductive kickback.Vary Ra, Rb and Ct with the controls given and see the change of frequency, period and duty cycle.
Astable Multivibrator with 555
This is a tutorial with calculator to help learn the application of 555 which is a very rare chip innovation. It is simple, versatile, flexible and programmable (by tweaking of pots).
Astable Multivibrato xml code
If you are starting with electronics, this is the first step. So do it now ! Do-It-Yourself.
Astable 555 Timer Flasher